Method of preparing nitro-cellu lose



. UNITED STATES PATENT rFicE.

GEORGE M. MOIVBRAY, OF NORTH ADAMS, MASSACHUSETTS.

METHOD OF PREPARING NlTRO-CELLULOSE.

SPECIFICATION forming part of Letters Patent No. 443,105, dated December23, 1890.

Application filed October 10, 1889. Serial No. 326,609. (No specimens.)

' To all whom it may concern:

Beit known that I, GEORGE M. MOVVBRAY, a citizen of the United States,residing at North Adams,in the county of Berkshire and State ofMassachusetts, have invented new and useful Improvements in the Art,Process, or Method of Manufacturing Nitro-Oellulose or Pyroxyline, ofwhich the following is a specification. 1

The present method of manufacturing pyroxyhne on alarge scale is toselect very line pure cotton tissue-paper, unsized, of a thicknesslessthan one five-hundredth of an inch, and nnmerse the same in a bath ofsulphuric and nitric acids of certain strength at a giventemperature-say about 85 Fahrenheitrfor about thirty minutes, to removefrom the acid bath, expel the adherent acid, plungebeneath cold water,and wash out all trace of acids by systematic flow of water. Fine purethin tissue-paper is selected because the instant the paper touches theacid bath it takes on a glutinous or colloid surface, which impedes thethorough conversion of the paper, thin as it is, and thus requires somethirty minutes, or thereabout to enable the conversion to take placethrough only one five-hundredth of an inch thickness. IVith thickerpaper treated in like manner only the surfaces of a sheet could benitrated, as the body of the paper would be unacted upon. Duringimmersion the paper has assimilated some forty per cent. of nitric acid,yet at the end of the operation it occupies less bulk than beforeimmersion, so dense and parchment-like has it become. It is thisproperty of the thin film of converted nitro-cellulose protecting thepaper beneath from chemical action that has led to selecting so fine apaper and demanded so long immersion, each of these factors adding tothe cost of the pyroxyline or gun-cotton.

My invention has for its object the reduction of cost of the crudematerials used by substituting a waste product-such as cotton rags,cottonseed lint from the hulls, &c. in lieu of high-priced unsizedtissue-paper now in use, lessening time now required for conversion, andwithal producing a better, because a more uniform, product. These results I attain by availing myself of a phys ical effect in crystallizinga salt (preferring nitrates) in the cells of the fiber as a preliminarystep to nitration, which opens up these cells to the action of the acidloath, whereby on immersion in the acid bath the sulphuric acid setsfree from the salt (if nitrate) nitric acid in a nascent state, whichinstantly acts chemically 011 the adjacent walls of each cell whereinthe nitrate has crystallized, and thus I effectnitration more rapidly,with less costly material, than is possible by the present method ofimmersing uusized tissue-paper in the usual mixed-acid bath, where theprocess of nitration is obstructed by the superficial glutinous film ofpyroXyline, which forms on the surface of the fibrous sheet of unsizedtissue-paperthe'instant it touches the acid bath.

I do not confine myself to the use of any particular form of cellulose,whether unsized paper, baled cotton, cotton yarn, or textile fabric, asin cotton rags, or even the cottonlint from cotton-seed hulls obtainedbydigester process, whether by treatment with sulphurous acid or bycaustic soda, or by simple cotton-lint from cotton hulls, as with anyone of these forms of cellulose fiber properly cleansed, bleached, andwashed, if impregnated with a salt not necessarily, but preferably, anitrate, a manufacturer can, by adopting my devices, make pyroxylinewith less costly cellulose and overcome the inconvenience of thatsuperficial glutinoushinderance to nitration hereinbefore described.

I have said it was not absolutely necessary to use a nitrate. I wish tobe understood by this assertion that any salt crystallized, or evenwater crystallized by freezing in the cells of fibrous cellulose,facilitates nitration by rendering the inner walls of cellular tissuemore readily accessible to the acids of the immersion-bath. Some saltsit might be necessary to remove after crystallization by washing, whilenitrates sodic nitrate, for i11- stance, for its low price, for itsready crystallization and yield of nitric acid evolved in the acid bathin contact with its sulphuric acid-I prefer to other salts.

To enable others skilled in the art to avail of my invention, I describeit for two varic- ICC) ties of pyroxylincvix., gun-cotton, and solublepyroxyline for plastic purposes, respectively.

For preparing textile cotton for explosive purposes use for one hundredparts of clean dry bleached rags three hundred parts of boiling waterand twenty-five to fifty parts sodic nitrate. l irst dissolve the sodicnitrate in pure clean water,heat to a boiling-point,and graduallyintroduce the rags, keeping up a moderate circulation of the mass untilno more air-bubbles leave the solution. Pass the rags through rollers toremove excess of saline solution. The operator may estimate that rags astheyleave the rollers in their wet condition will retain twice theirweight of sol ution. Thereforeeitherby weighing or deducting theproportion of liquid left in the tank he can calculate about thequantity of sodic nitrate taken up by the textile fiber. The rags fromthe impregnatingtank, having passed through the rollers, are now thrownonto frames protected from dust and allowed to dry gradually, in orderto enable the salt to penetrate by the action termed osmose into thecells of the fiber and there crystallize. They are then to be thoroughlydried and are ready for the mixed-acids-bath conversion intonitrocellulose.

The acids immersion-bath for gun cotton, (trinitro-cellulose,) as isknown in the art, should be as COl'lCOlltl'ZttQti as possible say forsulphuric acid, specific gravity 1.8;; for nitric acid, specific gravity1.5;, and in the proportion of sulphuric acid two parts, nitric acid onepart, both by weight.

For preparing soluble pyroxyline, (dinitrocellulosez) use of clean drybleached rags, one hundred parts; water, three hundred parts; sodicnitrate, from ten to twenty-five parts. The directions given forimpregnating, hereinbefore described, are to be observed here. Theproportions, however, of acids an d the strength of the acidsimmersion-bath differ; for example,sulphuricaeid,specificgravityl.8i5,sixtyseven parts; nitric acid, specific gravity 1.520,seventeen parts: Water, sixteen parts.

It is hardly necessary to remind one skilled in the artthat if linetissue-paper be used, because it is desired to avoid the fine opaquespecks found therein by the present process, a weak saline bath,consisting of ten parts of sodic nitrate to one hundred parts of paper,will snttiee, and that the drying of the paper should not be too rapid,so as to give time for &

the osmose action to take place.

llaving thus explained my process as I conceive the action to take placeand given a full, clear, and explicit description of the mode ofproceeding to obtain the advantageous results sought, what I claim inthe application, and desire to secure by Letters Patent, is

In the manufacture of the various grades ofnitro-cclluloseorpyroxyline,the followingprocess, consisting of threesteps: first, a preliminary impregnation ot' the cellulose material,whether simply fibrous, felted, or textile, by

crystallizing a salt, preferably sodic nitrate,

in the interstices of the cellulose material; second, immersing this drysaline impregnated cellulose material in a suitable bath of sulphuricand nitric acids, and, third, removing the intro-cellulose from thesaline-acids bath, washing outthe adherent acids, and drying theintro-cellulose, substantially as described, and for the purposes setforth. In testimony whereof I have affixed my nature in presence of twoWitnesses.

GEORGE M. MOWBRAY. Witnesses:

EDWARD Bnosson, J one CAnv.

